The present invention is concerned with slicing machines, and more particulary is directed to a novel method for automatically controlling the thickness of slices cut by a machine so as to produce a group of slices having a predetermined weight.
In the slicing of food products, for example the slicing of pork bellies into bacon strips, the slicing operation is carried out in a cyclic fashion. During each cycle a predetermined number of slices, forming a group known as a draft, are removed from the product. After one draft is sliced, the slicing operation is momentarily interrupted while this draft is carried away from the slicing blade, for example by a conveyor belt, and then the slicing of the next draft begins so that there is a discernible space between adjacent drafts.
The draft of the sliced product is typically sold according to weight. For example, bacon is often sold in one pound packages According to various regulations that protect consumer interests, a package of food that is sold according to weight must contain an amount of the food product that weighs at least the amount specified on the package. While it can contain more than the specified weight, from the producer's point of view it is desirable to maintain the amount of food product in the package as close to the specified weight as possible, without going under it, so as to avoid giving away excess amounts of the food product which can result in significant losses when the producer sells a large volume of the product.
Accordingly, various systems have been devised to automatically control the slicing of a food product so that the final draft of the product is as close to the desired weight as is practically possible One such system is disclosed, for example, in U.S. Patents Nos. 3,379,233 and 3,379,234. In the system disclosed in these patents, a partial draft of the food product is sliced and then the slicing operation is momentarily interrupted to weigh this partial draft. For example, if a one-pound package of bacon is intended to have 16 slices, the slicing operation will be halted several slices before the last slice is cut. The weight of this partial draft will determine the remaining amount of the product that is necessary to make up the one-pound package. The slicing operation is then resumed, with the number of slices and the thickness of each slice being controlled so as to provide the additional needed weight. The last several slices are cut on the basis of estimations of the thickness necessary to provide the final desired weight. While such a system may be capable of providing a final draft that is close to the desired weight, it will be appreciated that the need to interrupt the slicing operation during each draft results in a significant reduction of production capacity.
Another system which does not require the interruption of the slicing operation during the production of a draft is disclosed in U.S. Pat. No. 3,605,837. In the system of this patent, a curve, or more particularly a step function, is generated to indicate the desired weight of the slices after each slice is cut. For example, if a package of bacon weighing one pound is to be comprised of 16 slices, the desired weight would be incremented by one ounce for each slice. The actual weight of the slices is compared with the desired weight after each slice is cut, and any difference between the two is sent as an error signal to adjust the thickness of the subsequently cut slice.
A variation of this type of system is disclosed in U.S. Pat. Nos. 3,508,591 and 3,995,517. Basically, in the system disclosed in these patents, the weight of the slices that have been cut is extrapolated to calculate the predicted total weight of the package This predicted total weight is compared with the desired weight for the package, and any difference between the two is used to adjust the thickness of the subsequently cut slices.
While each of these latter two systems would theoretically appear to provide the desired result of producing a draft of slices that is at or near the desired weight, it has been found that they possess undesirable characteristics in actual practice. In the slicing of a food product such as bacon, the shape of the pork belly, i.e., its cross-sectional area, and the ratio of fat to lean in the slice affects its weight, for any given thickness. In addition, physical deformations in the belly, such as large wrinkles and voids, cause slice weight variations. Typically, the shape of the belly and the fat/lean ratio varies as the slicing operation progresses through the pork belly. Accordingly, if each slice in a draft is intended to have a nominal weight, its thickness will have to be varied as the ratio of fat to lean in the pork belly and its shape vary. In systems which operate in the manner of the latter two systems described above, which basically attempt to match the weight of the cut slices to an artifically generated curve, large variations in slice thickness can occur within a single draft if the ratio of fat to lean and/or the shape varies to any appreciable degree within the draft. Further, it is difficult, if not impossible, to achieve the desired final weight with any precision. Such variations in slice thickness are undesirable to the consumer, since, among other things, uniformity of cooking is difficult to obtain.